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HKAL Extra Exercise : Part 2 Matters
Chapter 8 Heat and Gas
8.1 Boyle’s Law
Ideal gas
1.
For smoke particles undergoing Brownian
motion in air, the motion of the smoke
particles is mainly caused by
A. collisions between air molecules.
B. collisions between smoke particles.
C. air convention currents.
D.
C.
D.
collisions between air molecules and
smoke particles.
molecules are negligible.
4.
2.
Which of the following statements about
an experiment showing the Brownian
motion with smoke particles in air is/are
correct ?
(1) The experiment makes it possible to
see the motion of the air molecules.
(2) The motion is caused by collisions
between air molecules and smoke
particles.
(3) The motion is irregular because the
motion of the air molecules is
irregular.
A. (1) only
B. (3) only
C. (1) and (2) only
D. (2) and (3) only
3.
Which of the following is NOT an
assumption in deriving the kinetic theory
of gases ?
A. The duration of a collision is
negligible compared with the time
between collisions.
B. Collisions with the walls of the
container and with other molecules
HKAL Extra Exercise Chapter 8 Heat and Gas
increase the average kinetic energy of
molecules.
The volume of the molecules is
negligible compared with the volume
of the gas.
Attractive forces between the
Which of the following is NOT a basic
assumption of the kinetic theory of an
ideal gas ?
A. All collisions are perfectly elastic.
B. All molecules are point particles that
have no physical size.
C. All molecules do not exert force on
one another during collisions.
D.
5.
All molecules move with a
distribution of speed at a certain
temperature.
Which of the following descriptions about
ideal gas is/are correct ?
(1) An ideal gas obeys Boyle’s law only
under high temperature and low
pressure.
(2) The internal energy of an ideal gas
consists of potential energy only.
(3) The molecules of an ideal gas have
no size.
A. (1) only
B. (3) only
C. (1) and (2) only
D. (2) and (3) only
1/14
Temperature and thermometer
6. The electrical resistance of a certain
8.
2
device is given by R = a + bt , where t is
the
temperature
indicated
by
a
Celsius-scale mercury thermometer, and a,
b are constants. If the device is calibrated
at 0 C and 100 C , how will its
performance, when used as a thermometer,
compare with that of the mercury
thermometer ?
A. It will give a lower reading at all
temperatures.
B.
C.
D.
It will give a lower reading
temperatures between 0 C
100 C .
It will give a lower reading
temperatures above 100 C .
It will give a lower reading
temperatures below 0 C .
for
and
for
The emf of a thermocouple E is measured
at a number of Celsius temperatureθ. E
andθare related by
E = aθ2 + bθ3, where a and b are
constants.
The above relationship can most easily be
verified by plotting a graph of
A. E/θ2 againstθ.
B. E/θ3 againstθ.
C. E againstθ2.
D. log E against logθ3.
9.
The calibration curve of a resistance
thermometer against a constant volume
gas thermometer is given below :
Resistance / 
1.6
for
1.5
1.4
7.
1.3
P
Q
1.2
1.1
0
R
0
R
The variations of properties P, Q and R of
three
different
substances
with
temperature may be used to define three
different
temperature
scales.
The
variations of P with R and of Q with R are
shown above. Which of the following
is/are correct ?
A.
C.
(1) Temperature scales defined in terms
of Q and R will agree at all points.
(2) Temperature scales defined in terms
of P and R will agree at all points.
(3) Temperature scales defined in terms
of P and Q will agree at all points.
(1) only
B. (3) only
(1) and (2) only
D. (2) and (3) only
HKAL Extra Exercise Chapter 8 Heat and Gas
0
20
40 60 80 100
Temperature / OC
When the resistance thermometer is left in
a room, its resistance is found to be 1.26Ω.
Find the value of room temperature on
both the resistance thermometer scale and
the gas thermometer scale.
Room temperature Room temperature on
on the resistance the gas thermometer
thermometer scale
scale/ C
/ C
A.
B.
C.
D.
16
cannot be
determined
16
32
16
32
32
cannot be
determined
2/14
The Celsius Temperature
10.
length / mm
120
100
P
80
Q
60
40
20
0
20
40
60
80
100 temp / OC
The graph shows the variations of the lengths of the liquid columns of two liquid-in-glass
thermometers with the temperature being measured on the ideal gas scale. What are the Celsius
temperatures obtained with these liquid-in-glass scales which correspond to 40 C on the ideal
gas scale?
Thermometer P Thermometer Q
Thermometer P
Thermometer Q
A.
40 C
56 C
B.
40 C
40 C
C.
4 C
56 C
D.
4
40 C
8.2 General Gas Law
General Gas Law
11.
N
5N
container X container Y
Container X holds N molecules of a certain
gas at atmospheric pressure. Container Y
has the same volume as X and holds 5N
molecules of the same gas. Both
containers are at the same temperature.
The ratio of the average number of
collisions per second with the walls in X to
those in Y is
A.
B.
C.
D.
1: 5.
5 : 1.
1 : 5.
5 : 1.
HKAL Extra Exercise Chapter 8 Heat and Gas
12. A cylinder containing air is fitted with an
airtight, frictionless piston maintained at a
constant temperature. The piston is moved
very slowly inwards, until the volume of
the cylinder has halved. Which of the
following quantities remains unchanged?
(1) The average force exerted by the gas
molecules on the piston.
(2) The average speed of the gas
molecules in the cylinder.
(3) The average momentum of the gas
molecules in the cylinder.
A. (1) only
B. (3) only
C. (1) and (2) only
D. (2) and (3) only
3/14
13. ‘The volume of a fixed mass of a real gas
at constant pressure is proportion to its
temperature.’ The statement above is true
only when
(1) a Celsius temperature scale is used.
(2) the gas is at a very low temperature.
(3) the gas is at a very high pressure.
A. (1) only
B. (2) only
C. (1) and (2) only
D. (2) and (3) only
14. The pressure of an ideal gas in a container
is P. If the number of gas molecules is
doubled, the volume of the container is
halved and the temperature is halved, the
pressure will be
A. P/2.
B. P/4.
C. 2P.
D. 4P.
15. Two equal closed vessels X and Y contain
different masses of an ideal gas. X has a
greater mass of the ideal gas than Y. When
the temperature T changes, which of the
following represents the variation of the
pressure P of the gas in each vessel with
temperature T ?
A.
B.
P
P
X
Y
Y
X
T / OC
C.
T / OC
P
X
Y
Y
X
T / OC
HKAL Extra Exercise Chapter 8 Heat and Gas
P
B
A
0
T
The graph shows the relation between the
pressure P and the absolute temperature T
of a fixed mass of an ideal gas, which
changes from state A to state B along the
path AB. Which of the following
statements is/are correct ?
(1) The volume V of the gas decreases.
(2) All the points on straight line AB
satisfy the relation
PV
= constant.
T
(3) The graph shows that P is directly
proportional to T.
A. (1) only
B. (3) only
C. (1) and (2) only
D. (2) and (3) only
17. An inexpansible vessel contains 1.4 kg of
gas at 600 K. What is the mass of gas
expelled from the vessel if it is heated
from 600 K to 700 K under constant
pressure ?
A. 1.2 kg
B. 0.86 kg
C. 0.2 kg
D. 0.14 kg
18. An inexpansible vessel contains air at
75 C . What percentage of air remains in
the vessel if it is heated to 100 C under
constant pressure ?
(You may take the ice point to be 273 K)
A. 63%
B. 75%
C. 78%
D. 93%
D.
P
16.
T / OC
4/14
19. An ideal gas is contained in a cylinder fitted with a light piston as shown below :
cylinder
IDEAL
GAS
piston
smooth
Initially, the piston is pushed outwards slowly. Afterwards, the piston is held fixed and the gas
is heated. Which of the following graphs represents the variation of gas pressure P with gas
volume V ? (i represents initial state; f represents final state)
A.
B.
C.
D.
P
P
i
P
i
P
f
V
f
i
f
f
V
V
i
V
Absolute Temperature
20. Theoretically, the zero on the absolute temperature scale is the point where a fixed mass of an
ideal gas has
(1) infinite volume.
(2) infinite pressure.
(3) infinite density.
A. (1) only
B. (3) only
C. (1) and (2) only
D. (2) and (3) only
Universal gas constant R
21. The equation of state for mass m of an ideal gas may be written pV = mrT. With reference to
this equation,
(1) if R is the molar gas constant, then the mass of each mole of this gas is R / r.
(2) the value of r is independent of the particular gas used.
(3) r depends of m.
A. (1) only
B. (3) only
C. (1) and (2) only
D. (2) and (3) only
22. What is the order of magnitude of the number of molecules in 1 cm3 of air in an atmospheric
pressure of 106 Pa and at room temperature ?
(Given : Universal gas constant = 8.31 J K-1 mol-1
Avogadro constant = 6.02 × 1023 mol-1)
A.
B.
C.
D.
1014
1017
1020
1026
HKAL Extra Exercise Chapter 8 Heat and Gas
5/14
Mixture of gases from two chambers
23.
25.
A
B
S
P1
P2
T2
T1
X
Y
S
6V
V
A and B are two identical containers
connected by a tap S initially closed. A
contains an ideal gas at a pressure P1 and a
temperature T1. B contains the same gas at
a pressure P2 and a temperature T2. The
Two metallic containers X and Y of
volume V and 6V respectively are
connected by a narrow tube as shown.
Initially the tap S is closed and an ideal
gas is contained in X at a pressure of 600
tap S is then opened. If the temperatures of
the containers A and B remain constant at
T1 and T2 respectively, the final pressure of
the gas mixture will be
kPa while container Y is evacuated. The
tap S is then opened and when equilibrium
is finally reached
A. there is no gas molecule moving
through the tap S.
B. the product of pressure and
volume of the gas in X is equal
to that in Y.
C. the gas molecules in Y on
average have the same speed as
A.
 P1 P2 
  T1  T2  .
 T1 T2 
B.
 P1 P2 
  T1  T2 
 T2 T1 
C.
D.
(P1T1 + P2T2) / (T1 + T2).
(P1T2 + P2T1) / (T1 + T2).
24. An ideal gas is contained in two metal
cylinders A and B connected by a tap,
which is initially closed. The volume and
pressure of the gas in the cylinders are as
follows :
pressure/Pa volume/m3
A 2 × 105
8 × 10-3
B
8 × 105
15 × 10-3
When the tap connecting the two cylinders
is opened, what will be the final pressure
in the vessel ? You may assume that the
temperature remains constant.
A. 2.0 × 105 Pa B. 5.0 × 105 Pa
C. 5.9 × 105 Pa D. 8.0 × 105 Pa
HKAL Extra Exercise Chapter 8 Heat and Gas
D.
those in X.
the gas pressure in X is 100 kPa.
26. Two vessels of equal volume both contain
an ideal gas and are connected by a tube of
negligible volume. Initially both vessels
are at temperature T0 and pressure P0. One
vessel is maintained at T0, while the
temperature of the other is raised to T. The
new pressure is then given by.
A.
B.
C.
D.
P0 (T + T0) / (2 T0)
2 P0 (T + T0) / T0
2 T P0 / (T + T0)
T P0 / (2T + 2T0)
6/14
8.3 Kinetic Theory of Gas
Root Mean Square Speed (r.m.s. speed)
27. A piston is SLOWLY pushed into a metal
cylinder containing an ideal gas. Which of
the
following
statements
is
INCORRECT ?
A. The mass of the gas remains the
same.
B. The number of the molecules per unit
volume remains the same.
C. The average speed of gas molecules
remains the same.
D. The pressure of the gas increases.
28. Container X holds pure nitrogen gas while
container Y holds pure hydrogen gas. If
the nitrogen molecules in X have the same
r.m.s. speed as the hydrogen molecules in
Y, which of the following conclusions may
be drawn?
A. The gas in Y has a higher temperature
than X.
B. The gas in X has a higher temperature
30. An ideal gas with molar mass m and has a
temperature T. For R be the universal gas
constant. The r.m.s. speed of its molecules
is
A.
RT
.
3m
B.
3RT
.
m
RTm
3
31. An ideal gas is at temperature T. If the
mass of a gas molecule = m, the molar gas
constant = R and the Avogadro constant =
NA, then the r.m.s. speed of the molecules
is
C.
RTm .
D.
A.
RT
.
mN A
B.
RTN A
.
m
C.
3RT
.
mN A
D.
RTN A
3m
32. A fixed mass of ideal gas at S.T.P.
than Y.
C. The gas in Y has a higher pressure
than X.
D. The gases in X and Y are at the same
temperature.
29. The root-mean-square speed of a sample
of helium gas molecules, each of mass m,
is c. Which of the following deductions is
correct ?
A. All molecules travel randomly with
occupies a volume of 3 m3. The gas is
heated and allowed to expand to a final
volume of 6 m3 with its pressure halved.
The root mean square speed of the gas
molecules is
A. increased four times.
B. unchanged.
C. halved.
D. reduced to one quarter of its
value.
speed c.
The percentage of molecules
traveling at speed c is greater than at
other speeds.
The average kinetic energy of the
molecules is 1 2 mc2 .
33. Two different gases A and B are contained
in two identical vessels. If the ratio of their
molecular
masses
and
absolute
temperatures are respectively 4 : 1 and 16 :
1, the ratio of their r.m.s. molecular speeds
will be
A. 1 : 2.
B. 2 : 1.
C. 4 : 1.
D. 8 : 1.
B.
C.
D.
The average speed of the molecules
is c.
HKAL Extra Exercise Chapter 8 Heat and Gas
7/14
34. Two different ideal gases, A and B, are
contained in two identical vessels. If the
37. A vessel of volume 4 × 10-3 m3 contains
0.32 g of an ideal gas at a pressure of 3 ×
ratio of their absolute temperature and the
ratio of the root-mean-square speed of the
molecules are respectively 2 : 9 and 2 : 3,
the ratio of their molecular mass is
A. 1 : 2
B. 2 : 1
C. 2 : 27
D. 27 : 2
105 Pa. The r.m.s. velocity of the gas
molecules is
A. 106 m/s.
B. 1 940 m/s.
C. 3 350 m/s.
D. 5 810 m/s.
35. The relative atomic mass of nitrogen is 14.
What is the ratio of the average speed of
nitrogen molecules N2 to that of hydrogen
38. At 27 C temperature and 1.00 × 105
molecules at room temperature ?
A.
D.
1/14
14
B.
E.
1/ 14
14
36. Identical containers A and B contain
hydrogen (H2) and nitrogen (N2)
respectively.
H2
N2
Container A
Container B
Both gases are at room temperature and
atmospheric pressure. Which of the
following statements is/are true ?
In both containers,
(1) the r.m.s. speed of gas molecules is
the different;
(2) the number of gas molecules is the
different;
(3) the frequency of collision of gas
molecules with the walls of container
is the same.
A. (1) only
B. (3) only
C. (1) and (2) only
D. (2) and (3) only
HKAL Extra Exercise Chapter 8 Heat and Gas
N/m2 pressure, the density of a gas is
0.141 kg/m3. The r.m.s. speed of the gas
molecules at 0 C will be
A. 464 m/s
B. 486 m/s
C. 1 390 m/s
D. 1 460 m/s
39. The r.m.s. speed of the molecules of a
certain gas X is 361 m s-1 at 287 K. Find
the molar mass of the gas X.
(Given : Universal gas constant R = 8.31 J
mol-1 K-1)
A. 19.8 g
B. 29.7 g
C. 36.6 g
D. 54.9 g
40. At 50 o C , the r.m.s. speed of the
molecules in a fixed mass of an ideal gas
is c. If the temperature is increases to
200 o C , the r.m.s. speed of the gas
molecules would become
A. 4c.
B. 2c.
C. 1.5c.
D. 1.2c.
8/14
Distribution of molecular velocity
41.
42.
N
0
N (c)
c
v
c
The above graph shows the distribution of
speeds (v) of the molecules in a constant
mass of gas. Which of the following
statements is/are correct?
(1) The peak of the curve drops when the
The graph shows the distribution of
molecular speeds c for a gas at room
temperature. N(c) represents the number
of molecules ΔN in a small range of
speeds c to c +Δc so that ΔN = N(c)Δc.
temperature rises.
(2) The value v = c at which the peak of
the curve occurs increases when the
temperature drops.
(3) Provided that the temperature does
not change, the kinetic energy of each
molecules is fixed.
A. (1) only
B. (3) only
C. (1) and (2) only
D.
As the temperature is decreased,
A. the peak position will move to
the left and its height will increase.
B. the peak position will move to
the right and its height will increase.
C. the peak position will move to
the right and its height will decrease.
D. the peak position and its height
will both remain unchanged.
(2) and (3) only
43. Which of the graphs best represents the distribution of molecular speeds in a gas at 250 K if
the dotted curve represents this distribution for the same gas at 500 K ?
A.
B.
C.
D.
fraction of
molecules
fraction of
molecules
0
speed
0
fraction of
molecules
fraction of
molecules
speed
0
speed
0
speed
Translational Kinetic Energy
44. An ideal gas is enclosed in a container at absolute temperature T. The absolute temperature is
now reduced to 0.5T, whilst the volume is kept constant. Which of the following statements
is/are correct ?
(1) The average separation of the molecules remains unchanged.
(2) The average kinetic energy of the molecules is halved.
(3) The average speed of the molecules is halved.
A. (1) only
B. (3) only
C. (1) and (2) only
D. (2) and (3) only
HKAL Extra Exercise Chapter 8 Heat and Gas
9/14
45. A fixed mass of gas at s.t.p. occupies a
volume of 2 m3. The gas is cooled and
allowed to expand to a final volume of 1
m3 with its pressure halved. The average
kinetic energy of the gas molecules is
A. increased four times.
B. doubled
C. halved.
D. reduced to one quarter of its
initial value.
46. Which of the following properties of
molecules of an ideal gas is/are the same
on the moon as on the earth, if the
temperature and volume of the gas are
unchanged ?
(1) The mass of a molecule of the gas.
(2) The average kinetic energy of a
molecule of the gas.
Internal energy of an ideal gas
48. According to the kinetic theory of gases,
at a given temperature, the molecules of
all gases have the same
(1) average intermolecular potential
energy.
(2) average speed.
(3) average momentum change when
they rebound from a wall of the
container.
A. (1) only
B. (3) only
C.
D.
(1) and (2) only
(2) and (3) only
(3) The average force acting on a
molecule when it rebounds from a
wall of the container.
A. (1) only
B. (3) only
C. (2) and (3) only
D. (1), (2) and (3)
47. Given :
Avogadro constant = 6 × 1023 mol-1
Boltzmann constant = 1.38 × 10-23 J/K
Molar gas constant = 8.31 J mol-1 K-1
If a mole of an ideal gas is heated under
constant pressure from 70 C to 30 C ,
the total kinetic energy of the gas
molecules is reduced by
A. 873 J.
B. 499 J.
C. 332 J.
D. 166 J.
49. The internal energy of an ideal gas at
temperature T is
constant. Given that R = the molar gas
constant, NA = Avogadro constant, k =
Boltzmann constant, then for an ideal gas
containing N molecules, the constant C is
equal to
A. NAR.
B. NAk.
C. NR.
D. Nk.
50. 1 mole of an ideal mono-atomic gas heats
at a constant volume of 0.01 m3 from a
pressure of 2 × 105 Pa to a pressure of 3
× 105 Pa. The increase in internal energy
of the gas is
A. 3 000 J.
C. 1 000 J.
HKAL Extra Exercise Chapter 8 Heat and Gas
3CT
, where C is a
2
B.
D.
1 500 J.
500 J.
10/14
8.4 Real Gases
van der Waals equation
51. Which of the following statements
concerning a real gas is/are correct ?
(1) The volume of the molecules cannot be
neglected.
(2) Intermolecular forces can be neglected.
(3) Collisions between molecules and the wall
of container are not perfectly elastic.
A. (1) only
B. (2) only
C. (3) only
53. When a gas is above its critical
temperature, which of the following is/are
correct ?
D. (1) and (2) only
52. The cirtical temperature of a substance is
the temperature
(1) at which the densities of its liquid
and saturated vapour are equal.
(2) above which the substance in its
gaseous phase cannot be liquefied by
the application of high pressure.
(3) at which solid, liquid and gaseous
(1) The gas cannot be liquefied by
applying pressure alone.
(2) Intermolecular forces are negligible.
(3) Collisions between molecules are
perfectly elastic.
A. (1) only
B. (1) and (2) only
C. (2) and (3) only
D. (1), (2) and (3)
8.5 Thermodynamics
Work done by a gas
54.
p / kPa
R
55. One mole of an ideal gas expands
isobarically at pressure P from absolute
temperature T1 to absolute temperature T2.
The work done by the gas is
PRT2
A.
B. Pln T2  ln T1 
T1
S
Q
P
0
phases of the substance can exist
together in equilibrium.
A. (1) only
B. (3) only
C. (1) and (2) only
D. (2) and (3) only
T/K
C.
Rln T2  ln T1 
D.
RT2  T1 
A fixed mass of an ideal gas goes through
56c. One mole of an ideal gas is contained in a
the three processes from P to S indicated
in the above p-T diagram: (1) : P → Q,
(2) : Q → R, (3) : R → S. During which
cylinder fitted with a light, frictionless
piston. The gas is expanded under constant
absolute temperature T so that its volume
increases from V to 3V and the final
pressure is P. If R is the universal gas
constant, the work done by the gas is
A. RT ln3/3.
B. RT ln3.
C. RT.
D. RT/3.
of the above processes is work done by the
gas on the surroundings ?
A. (1) only
B. (3) only
C. (1) and (2) only
D. (1) and (3) only
HKAL Extra Exercise Chapter 8 Heat and Gas
11/14
The indicator diagram
57.
58.
P / Pa
p / kPa
a
300
B
3 x 105
105
A
1
C
T1
T2
3
c
150 b
V / 10-3 m3
0
1 2
3
V / 10-3 m3
The figure above shows two curves for a given
mass of gas at temperature T1 and T2. If the
symbols P, V and T stand for the pressure,
volume and absolute temperature of the gas,
An ideal gas undergoes the processes
marked abc in the above p-V diagram. If
the total heat energy supplied to the gas
during the processes is 500 J, the change
which of the following statements is FALSE ?
A. No work is done by the gas when it
changes from state A to state B along the
line AB.
B. Temperature T1 is twice temperature T2.
C. When the gas expands from state B to
state C as represented by the curve BC, no
energy is transferred from the gas to the
surroundings.
D. To take the gas from state A to state C, 100
in internal energy of the gas will be
A. 800 J.
B. 300 J.
C. 200 J.
D. - 800 J.
J of energy is needed.
First Law of Thermodynamics
59. External work W is done on a real gas and
heat energy is only allowed to enter the
gas. If the change in internal energy of the
gas is ΔU, then
A. ΔU = 0.
B. ΔU < W.
C. ΔU = W.
D. W < ΔU.
60. The first law of thermodynamics can be
expressed asΔU = Q + W. When an ideal
gas is heated while keeping its volume
constant, which of the following holds ?
Q
ΔU
W
A.
B.
C.
D.
positive
negative
negative
positive
positive
negative
negative
positive
positive
zero
positive
zero
HKAL Extra Exercise Chapter 8 Heat and Gas
61. An ideal gas inside a container without
thermal insulation is expanded very slowly
to 110% of its original volume. While the
gas is being compressed, there is a heat
energy transfer of 4 000 J. Which of the
following statements is/are correct ?
(1) The
internal
energy
remains
unchanged.
(2) Heat energy is transferred out of the
system.
(3) Work done by the gas during
expansion is equal to 4 000 J.
A. (1) only
B. (3) only
C. (1) and (3) only
D. (2) and (3) only
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62. A fixed mass of an ideal gas is enclosed in
a cylinder by a piston. When the piston is
pushed slowly into the cylinder, which of
the following physical properties of the
gas will increase?
(1) temperature
(2) pressure
(3) internal energy
A. (1) only
B. (2) only
C. (1) and (2) only
D. (2) and (3) only
63. In which of the following cases will heat
always flow into a body X ?
(1) X is changed from its liquid state to a
gaseous state at condensation point.
(2) X is in thermal contact with another
system which has a smaller amount
of internal energy.
(3) X is in thermal contact with another
system at a higher temperature.
A. (1) only
B. (2) only
C. (1) and (3) only
D.
64.
p / kPa
C
B
A
0
T/K
A fixed mass of an ideal gas undergoes the
process ABC as shown in the
pressure-temperature diagram. Which of
the following deductions from the diagram
is incorrect ?
A. Work is done on the gas by the
surroundings when it changes
from B to C.
B. The volume of the gas at C is
smaller than that at B.
C. Work is done by the gas when it
changes from A to B.
D. Heat energy is transferred to the
gas when it changes from A to
B.
(2) and (3) only
Isothermal Process
65. The internal energy of an ideal gas always
changes when
(1) it is expanded in an insulating container.
(2) its volume increases.
(3) it undergoes an isothermal change.
A. (1) only
B. (3) only
C. (1) and (2) only
D. (2) and (3) only
66. One mole of an ideal gas of volume V1 is
at an initial pressure P1 and temperature T1.
If the gas undergoes an isobaric expansion,
so that its volume increases to V2.
(1) the internal energy of the gas increases.
(2) the external work done is equal to P1V1
ln(V2 / V1).
HKAL Extra Exercise Chapter 8 Heat and Gas
(3) there is heat exchange between the gas and
the surroundings.
A. (1) only
B. (3) only
C. (1) and (3) only
D. (2) and (3) only
67. For an ideal gas contracted isothermally,
A.
B.
C.
D.
the work done on the surroundings is
zero.
the heat energy transferred to the gas
is zero.
the work done on the gas is equal to
the heat energy rejected by it.
the internal energy of the gas
increases.
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Isobaric Process
68. The energy which must be supplied to 1 mole of gas initially at absolute temperature T,
pressure p and volume V, to raise its temperature by 1 K, is Q1 at constant volume and Q2 at
constant pressure. The value of Q2 is
A. Q1 + pVT.
B. Q1 + pV/T.
C. Q1 – pVT.
D. Q1 – pV/T.
Cycle
69. An ideal gas is taken through the series of
changes shown.
volume V change as shown in the p-V
diagram below.
pressure
P / 105 Pa
4
70. A fixed mass of an ideal gas undergoes a
cycle ABCD in which its pressure p and
P
B
A
B
D
2
A
C
0
volume V / m3
0
2
4
6
8
10
Which of the following statements is/are
correct ?
(1) The gas has the same temperature at
B and at C.
(2) The work done by the gas during the
change AB is equal to that done on
the gas during the change CD.
(3) No net work is done by the gas in
completing one cycle.
A.
B.
C.
D.
KEY :
C
D
V
Which of the following statements is/are
correct ?
(1) From A to B, the internal energy of
the gas increases.
(2) From B to C, heat is flowed into the
gas.
(3) From C to D, work is done on the
gas.
A. (1) only
B. (3) only
C. (1) and (2) only
D. (2) and (3) only
(2) only
(3) only
(1) and (2) only
(2) and (3) only
1 – 10 : DDBCB, BAACA, 11 – 20 : CDBAC, CCDAB, 21 – 30 : ADDCC, CBBCB
31 – 40 : CBBAB, ACCDD, 41 – 50 : AADCD, DBADB, 51 – 60 : ACDBD, ADCDD
61 – 70 : CBCCA, CCBAC.
HKAL Extra Exercise Chapter 8 Heat and Gas
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